In this November 2, 2017 photo, Mathew Fulkerson and his wife Leigh Ann pose at their Subterra Airbnb located in a former underground missile silo base near Eskridge, Kan. It was designed to house a nuclear warhead six decades ago – but now, this Cold War silo is the perfect spot for a mini break at just $133 a night. (Photo by Thad Allton/The Topeka Capital-Journal via AP Photo)

A camel is pictured in front of the Saturn tracking complex at the Russian-leased Baikonur cosmodrome in Kazakhstan on October 9, 2018. An astronaut and cosmonaut are due to travel to the ISS on October 11 aboard a Russian Soyuz MS-10 spacecraft from the Baikonur Cosmodrome in Kazakhstan. (Photo by Kirill Kudryavtsev/AFP Photo)

Yakutsk, with a population of around 270,000, holds its own title: that of the coldest city on Earth. Here: Frost-encrusted house in the city centre. (Photo by Amos Chapple/Courtesy Images/RFE/RL)

Electric cars sit charging in a parking garage at the University of California, Irvine January 26, 2015. “The Irvine Smart Grid Demonstration”, a $79 million project funded half by federal stimulus money and half by Edison and partners like UC Irvine, was launched in 2010. The $12 billion utility's research team Southern California Edison is testing everything from charging electronic vehicles via cell phone to devices that smooth out the power created by rooftop solar panels. Those are some of the roughly 60 projects in the works at Edison's Advanced Technology division. It has a small $19 million annual budget, but its influence far exceeds that. (Photo by Lucy Nicholson/Reuters)

A toddler sits on the winner of the giant pumpkin category during the RHS (Royal Horticultural Society) London Harvest Festival Show at RHS Lindley Halls on October 6, 2015 in London, England. The traditional harvest themed show runs October 6-7 and showcases a wide range of late summer grown fruit and vegetables. (Photo by Ben Pruchnie/Getty Images)

Storks casts shadows as they search for food on the dried-up Lake May in southwest Turkey on October 30, 2021. (Photo by Seyit Konyal/Solent News)

Vietnam’s Son Doong cave, the largest in the world, could hold a 40-story skyscraper inside. The pristine ecosystem has its own river and jungle. Despite its size, Son Doong wasn’t discovered until 1991. It was lost again for nearly two decades and was fully explored for the first time in 2009. (Photo by Jason Speth/HuffPost)

Britain's Catherine, Duchess of Cambridge, shelters from the rain under an umbrella as she arrives at the London School of Economics to mark the launch of The Royal Foundation Centre for Early Childhood, where she took part in a roundtable discussion on the Centre's inaugural report, “Big Change Starts Small” which was released today, in London on June 18, 2021. (Photo by Richard Pohle/Pool via AFP Photo)